<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body{
            background-color: #000;
        }
        a {
            text-decoration: none;
            color: #666;

        }

        a.button {
            width: 160px;
            height: 50px;
            background-color: #333;
            display: block;
            text-align: center;
            line-height: 50px;
            border-radius: 5px;
            margin: 100px;
            position: relative;
            overflow: hidden;
            z-index: 0;
        }
        a.button::before{
            content: "";
            display: block;
            width: 200px;
            height: 200px;
            /* background-color: red; */
            background-image: radial-gradient(yellow,transparent 60%);
            position: absolute;
            left: -50px;
            top: -50px;
        }
        a.button::after{
            content: "";
            position: absolute;
            left: 2px;
            top: 2px;
            bottom: 2px;
            right: 2px;
            background-color: #333;

        }
        a.button span{
            position: relative;
            z-index: 1;
        }

        a.button:hover span{
            color: khaki;
        }
    </style>
</head>

<body>
    <a href="" class="button"><span>加入购物车</span></a>
</body>

</html>